A continuous sheet of paper, such as printout paper for computers, is usually provided with perforations at its opposite edges and is transported by a traction device having projections engageable in the perforations. This method of transport, which is called "traction feed", has the advantage that the continuous sheet can be transported smoothly without zigzagging.
In copying machines of this type, images are formed on a continuous sheet of paper which is being fed by the traction device. Such images are formed, for example, by an electrophotographic process. The electrophotographic process comprises the steps of forming a latent electrostatic image on a photosensitive member, developing the latent image with toner to obtain a toner image and transferring the toner image onto the paper.
The traction feed method, nevertheless, has the problem that the paper releases particles of paper at the traction device because the paper is perforated. These particles get into some of the other units and impair the performance thereof, possibly resulting in a malfunction of the units.
The conventional traction feed method has another drawback in that the continuous sheet of paper must be set in place by a very cumbersome procedure, i.e. by passing the sheet around the traction device and properly engaging the projections of the device in the perforations of the sheet. To eliminate the above drawback, it is possible to make the traction device substantially completely retractable from the image forming zone, but this requires a large space which makes the overall size of the machine large.
Accordingly it would be desirable to have a traction device which occupies only a small space and onto which the continuous sheet can be set easily. However, since the sheet must be set onto the device in the vicinity of the image forming zone, care must be taken to avoid possible damage to the image forming assembly, e.g. the photosensitive member, that could result when a tool or the like strikes against the assembly.